Many industrial processes require the use of valves for the cycling of flow streams. Such processes include drying, adsorption, gas sweetening and fume incineration. These processes generally employ some type of fluid moving equipment such as pumps, blowers and/or compressors as well as the numerous valves necessary to direct the gas flow to the appropriate vessel at the appropriate time.
The selection of appropriate valves for cyclic processes depends upon a number of criteria. These include flow, operating and sealing characteristics, port configuration, physical size, energy input (e.g. electrical, hydraulic or pneumatic) and cost. Because such processes typically employ relatively low pressures (e.g. in the range of 1 psia to 100 psia), large volumetric flows result. In such situations, it is therefore necessary to have an accompanying low pressure drop, on the order of 0.05 psi to 2 psi.
Valve operating characteristics include quick opening and closing times, on the order of 0.25 to 2 seconds. Sealing characteristics include the type of seal, the mating surfaces, and the power required to open and close the valve to prevent any leakage during the full-closed position. As to port configuration, it is noted that a majority of valves handle a single fluid, and consequently these have one port for entry of fluid and one port for exiting of fluid.
Multiples of this type of valve have long been used for the control of cyclic processes, as given their nature, numerous valves are required. It is necessary to interconnect these valves thus requiring extensive interconnecting piping. In order to maintain a low pressure drop with the use of dual valves, relatively large valve sizes are required (e.g. greater than 10 inches in diameter), resulting in relatively slow open/close times and high costs.
Kice, in U.S. Pat. No. 3,489,178 teaches a valve design with both inlet and outlet directions perpendicular to the axis of rotation. This design does not utilize a large portion of the outer diameter of the valve, thus requiring a valve of increased size and cost.
Tucker, in U.S. Pat. No. 2,312,941 teaches a valve having very small clearances to seal the ports having different pressures. This requires an oversized valve body at additional expense. Further, the inertia associated with the thick walled valve drum causes an increase in valve response time and consequently excessive operating costs.
Thus, there is a need in the art to improve valve design to more nearly meet all of the criteria for cyclic service.